1. Field of the Invention
The present invention relates to a pantograph jack apparatus for elevating the body of a motor vehicle, for example, to change a tire. In particular, the present invention relates to a pantograph jack apparatus that is easily set under a predetermined location on the motor vehicle body.
2. Description of Related Art
A conventional pantograph jack apparatus, such as that shown in Japanese Pat. No. 51-45860, is shown in FIGS. 1 and 2. Conventional pantograph jack 15 includes base plate 9 and supporting plate 8 connected by a pair of upper arms 7a, 7b and a pair of lower arms 7c, 7d. Supporting plate 8 includes specially shaped jacking portion 8a, which engages with a complementary jacking portion located on the body of the motor vehicle. Upper arms 7a, 7b are pivotally connected to supporting plate 8 by pins 10, and lower arms 7c, 7d are pivotally connected to base plate 9 by pins 11. Upper arm 7a is pivotally connected to lower arm 7c by pin portions (not shown) of connecting nut 6. Upper arm 7b is pivotally connected to lower arm 7d by pin portions (not shown) of connecting bearing 5. Shaft member 1, which includes threaded portion 1a and non-threaded portion 1b, connects connecting nut 6 to connecting bearing 5.
As shown in FIG. 2, non-threaded portion 1b of shaft member 1 includes first stop portion 3a and second stop portion 3b, which prevent connecting bearing 5 from moving relative to shaft member 1 in the axial direction. Connecting bearing 5, however, can rotate about non-threaded portion 1b of shaft member 1 and is prevented from binding on the end of shaft member 1 by ball bearing 13. Operating member 4 is connected to the non-threaded end of shaft member 1.
Connecting nut 6 is threaded on threaded portion 1a of shaft member 1 so that, as is well known in the art, when operating member 4 is rotated by a crank handle (not shown), shaft member 1 rotates, causing connecting nut 6 to move either toward or away from connecting bearing 5 through the cooperation of the threaded bore of connecting nut 6 with threaded portion 1a of shaft member 1. When connecting nut 6 moves toward connecting bearing 5, supporting plate 8 is raised relative to base plate 9 by the well known pantograph action.
When not in use, conventional pantograph jacks, such as that shown in FIGS. 1 and 2, are normally stored in the motor vehicle in their lowered position, that is, with upper arms 7a, 7b approximately parallel to lower arms 7c, 7d, which is achieved by rotating operating member 4 and shaft member 1 to produce a maximum separation between connecting bearing 5 and connecting nut 6 and a minimum separation between supporting plate 8 and base plate 9.
When conventional pantograph jack 15 of FIGS. 1 and 2 is put in use to raise the motor vehicle body, base plate 9 first is positioned on the ground approximately beneath the jacking portion of the motor vehicle body, and supporting plate 8 then must be raised by rotating operating member 4 and shaft member 1 to engage jacking portion 8a with the complementary jacking portion of the motor vehicle body.
Raising supporting plate 8 by rotating operating member 4 while simultaneously positioning jacking portion 8a to properly engage the jacking portion of the motor vehicle body, however, has proved to be a cumbersome operation. The operator's attention must be divided between two portions of the pantograph jack, operating member 4 and supporting plate 8. Raising supporting plate 8 to the initial engaging position with the jacking portion of the motor vehicle by rotating operating member 4 also is a very time-consuming process because, to insure proper mating of jacking portion 8a to the jacking portion of the motor vehicle body, operating member 4 must be turned by hand. If the operator chooses to save time by turning operating member 4 with its complementary crank, the operator will be too far removed from supporting plate 8 to see whether jacking portion 8a is properly mating with the jacking portion of the motor vehicle body.
The present invention is intended to provide an improved pantograph jack that eliminates the problems of conventional pantograph jacks. In particular, the present invention is intended to provide an improved pantograph jack that enables the operator to raise the supporting plate and engage its jacking portion with the jacking portion of the motor vehicle body without rotating the operating member and shaft member of the pantograph jack.
Additional advantages of the present invention will be set forth in part in the description that follows and in part will be obvious from that description or can be learned by practice of the invention. The advantages of the invention can be realized and obtained by the apparatus particularly pointed out in the appended claims.